The present invention relates to new footwear compensating the foot to its environment.
The natural foot is angulated somewhat upward from the horizontal from its lateral side. The foot is inverted, or tilted, so that the plantar surface of the foot faces slightly toward the midline of the body and away from a transverse plane. In this regard, the foot and lower leg are still in a slightly varus attitude, generally bent inward, not unlike their position in the classical in utero fetal position.
The median sagittal plane is the midline of the body, which divides the body into equal right and left halves and touches the floor at a position midway between two parallel feet when the body is in an erect anatomical position. The foot also has a median sagittal plane which divides each foot into equal medial and lateral (left and right) halves or aspects. A sagittal plane itself is a flat plane passing through the body while in an erect anatomical position. The plane passes through the body in an anterior-posterior direction and divides the body into right and left parts, where the body is erect and the feet are parallel. A transverse plane is a flat, horizontal plane that lies parallel to the horizon and passes through the body in an erect anatomical position and which divides the body into superior (upper) and inferior (lower) parts.
The normal longitudinal axis of motion of the foot is a line that represents the ideal physical relationship of the osseous segments of the foot as they relate to foot function. The normal longitudinal axis of motion also indicates the preferred direction of vector forces generated through the foot for the production of maximum and optimum efficiency of foot function during static stance and locomotion. The longitudinal axis of motion and the median sagittal plane of the foot are normally in close proximity. The more closely that these two clinical entities are correlated and aligned; the more closely one achieves the ideal biophysical criteria for normal position, motion and function of the foot.
The foot and lower legs themselves have an inverted angulation which is residual from their fetal growth. In this regard the heel, (rearfoot), is slightly inverted to the transverse (horizontal) plane, approximately 4 degrees plus or minus amounts up to 2 degrees, on the average. This is commonly referred to as rearfoot or subtalar joint varus. The forefoot is inverted, additionally, to the rearfoot by an added amount of approximately 8 degrees plus or minus amounts up to 6 degrees, on the average. This is commonly referred to as forefoot or midtarsal joint varus. The lower legs are also slightly inverted to the ground by approximately 4 degrees plus or minus amounts up to 2 degrees, on the average, and this deviation is referred to as tibial or genu varum.
A weight-bearing foot on a flat surface, a horizontal flat plane, tends to pronate abnormally and excessively in order to compensate for these inverted angulations.
Excessive pronation is considered to be the unnatural position, motion, and function that the foot assumes when the foot is required to go through an excessive amount and range of motion in order to compensate for inherent anatomical variations or other planal predominances of the foot from flat surfaces. The weight-bearing vector forces of excessive pronation are generated more medially and away from the longitudinal axis of motion and the midline of the foot and are directed more toward the midline of the body.
Pronation is actually a complex simultaneous triplane motion generally in the direction of abduction, eversion and dorsiflexion. The axis of this motion passes through the foot from the posterior, lateral and plantar portions of the foot to the anterior, medial and dorsal portions of the foot.
The motion of normal pronation generally passes along the longitudinal axis of motion of the foot. A smooth movement of the foot, with a minimum of pronation occurs when weight-bearing forces directed through the foot pass closer to the longitudinal axis of motion and the median sagittal plane of the foot as the foot moves through the various stages of its gait.
An amount of rearfoot and forefoot pronation itself, (approximately 4 degrees to 6 degrees) is considered normal and is necessary for the foot to act as an effective shock absorber. Beyond that accepted amount, rearfoot and forefoot pronation is considered to be abnormal, excessive, and not within an acceptable range of motion.
Since nearly all individuals within the general population possess many different degrees of variations of foot types and amounts of abnormal pronation, ranging from slightly excessive to extremely excessive; it is the purpose and intention of the present invention to compensate for as much of these varying amounts that are in excess of the normal amount of allowable foot motion by prohibiting those additional amounts to occur. Excessive amounts of pronation usually fall within the range of from 2 degrees of 14 degrees of additional motion; that is, motion which is in excess of the allowable amount of 4 degrees to 6 degrees of normal motion (normal pronation). The excessive pronation of the weight-bearing foot on a flat surface comes about when the normal foot, which off weight-bearing, is slightly inverted, attempts to come down to meet and align itself with the ground (flat surfaces). In order to accomplish proper support, balance, equilibrium and ultimately propulsion, the rearfoot is required to follow the motion and action of the forefoot down to meet the ground from the inverted position and thus the entire foot pronates excessively. More specifically, the rearfoot goes through an excessive range of motion to allow this function and motion of the forefoot to occur due to the fact that rearfoot stability is dependent upon the structure and stability of the forefoot and vice versa. Ideally, the weight-bearing foot should be in its natural inverted plane at the time when it makes full contact with the surface upon which the foot bears and when it is fully weight-bearing.
Podiatric literature and the art of footwear deal with the foot in terms of the foot having abnormality in pronating excessively. Contrary to prior thought, whereby most feet were considered to be deviations of a "normal" foot type; abnormality actually resides in the fact that modern civilization and man's technological environment has provided unyielding, horizontal, flat surfaces for the foot and the footwear to adapt to; whereas, the natural, still-contoured foot is more suitably adapted to a pitched (inverted) surface environment. The foot, which is still in a period of evolutionary transition toward more efficient, upright bipedal locomotion, is consequently at a functional disadvantage, and to apply the inner border of the forefoot to a hard, flat walking or running surface; most individuals must pronate excessively. The modern human foot is, therefore, not suitable for use on a flat surface without some modification of the surface.
The present invention is for footwear which allows the foot to function in its natural inverted environment with the footwear adapted to the environmentally flat surface while the foot is able to comfortably be positioned in its natural position.
In the past, some recognition has been given to the angulation of feet, and particularly with regard to running shoes. The prior art concerned itself with changing the angular relationship between the heel and a flat surface. Subotnick in his U.S. Pat. No. 4,180,924 attempted to improve footwear by providing a running shoe with a wedge at the heel portion of the footwear. The wedge tended to compensate the heel to react to a flat surface in its attempt to avoid some excessive pronation. The emphasis seems to have been placed on compensating the heel since the heel in walking or running usually makes the first contact with the ground and is the area where excessive pronation is most obviously noticed.
Block in his U.S. Pat. No. 4,262,435 also discloses a compensated heel. Both Subotnick and Block substantially ignore compensating footwear at the forefoot and its relationship to excessive pronation.
It should be noted that Subotnick provides a transverse beveled sole tapering from the heel, past the arch, to its ending point, located immediately to the rear of the metatarsal-phalangeal joints (the ball of the foot). By the same token, Block's sole piece also has a relatively thickened body extending from the heel counter, forwardly and downwardly, and ending its taper also behind the metatarsal-phalangeal joints (the ball of the foot).
Footwear compensations of the past have attempted to correct the inverted heel, or otherwise have attempted to stabilize the rearfoot and thereby hoped to restrict or eliminate excessive pronation of the rearfoot. Such compensation, however, ignores the inverted forefoot which actually, and in fact, causes the resultant inward rolling and tipping of the subtalar and ankle joints (excessive rearfoot pronation) as the rearfoot rolls medially and everts following the movement of the inverted forefoot down to the ground.
It should be noted that in the prior art, compensation of the heel, while providing a substantially horizontal impact of the heel to a flat surface, does not compensate the inverted position of the forefoot, which, according to the prior art, still was subject to excessive pronation. Most rearfoot compensations of prior art shoes, in fact, tend to restrict the rearfoot's own natural inverted planal predominance that would otherwise allow the rearfoot to pronate amounts in order to act as an effective shock absorber when coming in contact with the ground.
According to the present invention new footwear is provided compensating the foot's natural angulation by providing an angulated sole sloping upward from the lateral aspect of the forefoot to the medial aspect, compensating the forefoot along the base and shafts of the metatarsal bones diagonally, the metatarsal-phalangeal joints (the ball of the foot), and the toes, giving the area beneath the first metatarsal-phalangeal joint (the big toe joint) the greatest elevation.
It has been found that the angulated wedge-shaped sole of the footwear of the present invention aligns the foot by compensating to angulate the forefoot to the heel and as a result, the entire foot to the ground for proper weight-bearing and even weight distribution. That is, the angulated wedge-shaped sole in the present invention compensates the forefoot and by so doing, whether the foot is standing still or in normal walking or running gait, weight-bearing forces directed through the foot pass closer to the median sagittal plane and the normal longitudinal axis of motion of the foot from rearfoot to forefoot. The footwear of the present invention compensates the foot to modern civilization's usually flat surfaces.
The advantages of the footwear of the present invention are that whether for normal standing, walking or for running, the footwear is adapted to the flat surface while the foot is maintained in its natural position. In standing, walking or running, excessive pronation is reduced, controlled or eliminated; the foot acts as a more immediate and effective fulcrum and lever for the walking or running step with the minimum waste of movement and distortion of the natural foot; and impact shock to the foot and the entire skeletal complex is minimized as the foot functions more efficiently and as a more effective shock absorber. The forward movement of the foot from the strike of the heel in its normal gait in walking or running proceeds to a flat contact of the footwear of the present invention with a flat surface during its fully weight-bearing midstance phase of gait; while the foot itself, having a minimum of pronation, functions at its optimum since the footwear itself has been adapted to the flat surface.
The footwear of the present invention has a more even and harmonious contact with a flat surface and the push-off phase of the gait is more firmly focused on the first metatarsal-phalangeal joint (big toe joint) with the weight-bearing gravitational forces being more evenly directed through the foot for most optimum, efficient, and effective standing, walking, or running. In addition to the vast majority of individuals with varsus (inverted) foot and leg types (approximately 95 percent of the entire population) who would benefit from the advantages of the present invention; firmly focusing the propulsive forces on the first ray segment of the foot becomes a distinct and added advantage to those individuals who also possess the anatomical variation of hypoplasia (shortness) of the first metatarsal bone (which clinical entity is seen in approximately another 60 percent of the general population).
It has been found that, on the average, 4 degrees to 8 degrees of angulated compensation of the forefoot from the lateral aspect of the footwear to the medial aspect of the footwear seems to be preferred. The area of compensation angulates and slopes upward and toward the medial aspect of the footwear in all directions from its vertex at the area beneath the lateral aspect of the fifth metatarsal-phalangeal joint. It then radiates from proximally to distally from this vertex and at the same prescribed angle to encompass the following areas of the forefoot: (1) the area beneath the base if the fifth metatarsal bone; (2) the area diagonal to the longitudinal and transverse arches of the foot and shafts of the metatarsal bones; (3) the areas beneath the five metatarsal-phalangeal joints (the ball of the foot); (4) the area beneath all of the toes.
Compensating between 8 degrees plus or minus amounts up to 6 degrees provides good results at the medial aspect of the footwear. This provides an angular range and sets parameters of not less than 2 degrees nor more than 14 degrees of forefoot varus compensation. For example, a sole of a shoe of a particular size, width, and style may slope from a thickness of 3/8 of an inch greater on the medial aspect at the forefoot of the footwear to the lateral aspect at the forefoot of the footwear providing an 8 degree angle; while in yet another shoe of a different size and width, the sole of this same style shoe, may slope from this same thickness of 3/8 of an inch greater on the medial aspect than on the lateral aspect at the forefoot of the footwear providing yet a different angle. This is also true in examples where the angle of the forefoot compensation remains constant while the thickness achieved at the medial aspect varies; again depending on the size, width, and style of the particular footwear. In each and every example, however, the relative thickness of the forefoot compensation at the medial aspect of the footwear is always thicker than that at the lateral aspect of the forefoot of the footwear by the prescribed amount.
In effect, for such shoes, 3/8 of an inch, plus or minus, amounts up to 5/16 of an inch usually provides angular equivalents of 8 degrees plus or minus amounts up to 6 degrees. An angular range of from 2 degrees to 14 degrees of forefoot varus wedge compensation or a dimensional range of from 1/16 of an inch to 11/16 of an inch (approximately 0.16 centimeters to approximately 1.74 centimeters) of thickness, greater on the medial aspect than on the lateral aspect of the forefoot; would, under most circumstances, achieve the desired results.
These parameters are necessary and adviseable in order to be able to gradually introduce the novel and revolutionary concept of the present invention into widespread usage among the general population; since it is often necessary to gradually increase the amount of forefoot varus wedge angulation in moderate increments, slowly, and over a gradual period of time in order of effectively achieve greater compliance and acceptance of the concept with fewer side effects, less discomfort, and shorter periods of adjustment.
It may also be necessary and adviseable for certain individuals to be afforded the opportunity to obtain different, varying, and/or graded amounts of forefoot varus compensation in a manner similar to the present day shoe size and width selections or in the form of prescription footgear when their particular needs fall outside of the usual and customary 4 degrees to 8 degrees average range of inverted forefoot varus angulation.
The sole of the footwear of the present invention is also beveled from the heel down toward the toes on the lateral aspect. This longitudinal bevel created by the taper of the wedge of the forefoot compensation of the present invention is similar to the effect of the conventional heel lift. Thus whether in walking or running as the footwear makes contact with the ground starting at the heel, the footwear moves forward with generally flat, smooth, the congruous impact with a flat surface. This longitudinal bevel effectively creates even greater heel lift and elevation of the rearfoot in addition to that of the conventional heel lift. This further reduces the weight on the heel and decreases heel, foot, leg, and back discomfort when one is standing still. This feature additionally tends to enhance the conventional heel lift by propelling the body forward during the act of locomotion, thus adding to the increased efficiency of walking or running, and producing faster walking or running elapsed times so important to the competitive athlete. This feature is also more consistent and compatible with the evolutionary trend toward increased equinus of the human foot; a theory proposed by careful observes in the fields of organic evolution and physical and cultural anthropology.